Add this code to your themes functions.php file. It will remove only that message. It should trigger on just the pages where it is likely to occur.
function remove_added_to_cart_notice()
{
$notices = WC()->session->get('wc_notices', array());
foreach( $notices['success'] as $key => &$notice){
if( strpos( $notice, 'has been added' ) !== false){
$added_to_cart_key = $key;
break;
}
}
unset( $notices['success'][$added_to_cart_key] );
WC()->session->set('wc_notices', $notices);
}
add_action('woocommerce_before_single_product','remove_added_to_cart_notice',1);
add_action('woocommerce_shortcode_before_product_cat_loop','remove_added_to_cart_notice',1);
add_action('woocommerce_before_shop_loop','remove_added_to_cart_notice',1);
I've pasted this answer from my own answer at Remove/Hide Woocommerce Added to Cart Message but Keep/Display Coupon Applied Message